Recurrent Focal Myositis in Childhood: A Case Report and Systematic Review of the Literature

Recurrent focal myositis developing into a generalised idiopathic inflammatory myopathy with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase autoantibodies

“…Histopathology and immunohistochemistry on muscle biopsy cannot accurately distinguish between focal myositis and generalised IIM. More recently, serological testing –based on the detection of MSAs that are not found in focal myositis as seen at the first stage of the disease in the case presented here has helped clinicians in diagnosing and characterising generalised IIM according to distinct clinicoserological profiles 1 2 9 12. Indeed, it has been found that PM–the patients who developed generalised IIM following focal myositis described earlier were diagnosed with PM–is a rather heterogeneous group of diseases, encompassing a variety of distinct IIM subtypes (IMNM, antisynthetase syndrome, non-specific myositis/overlap myositis) and even untreatable muscle diseases such as inclusion body myositis and muscular dystrophies 13 14.…”

“…Focal myositis is an inflammatory disorder restricted to one (or more adjacent) skeletal muscle(s) with a benign, that is, mostly self-limiting disease course 1 2 8. In contrast, generalised IIM–of which IMNM/IIM with anti-HMGCR Abs is a subset–are characterised by proximal (axial and limb-girdle) muscle weakness and often require multimodal immunosuppressive treatment 3 9 10.…”

“…However, it seems there is pathophysiological and clinical overlap between focal myositis and generalised IIM, as illustrated by reports of patients who developed generalised polymyositis (PM) following focal myositis 11. A variety of biomarkers may aid the clinician in distinguishing focal myositis from generalised IIM and identifying patients with focal myositis at risk of developing a generalised IIM 1 2. First, conventional laboratory markers such as serum CK activity, erythrocyte sedimentation rate (ESR) and C-reactive protein are atypical for focal myositis; indeed, earlier reports described a higher risk of development of generalised IIM in patients with focal myositis who also had abnormal serum CK activity or ESR.…”

“…While focal myositis is considered to be a relatively benign disease in which glucocorticoid monotherapy generally suffices, generalised idiopathic inflammatory myopathy (IIM) often necessitates multimodal immunosuppressant treatment 1–3. Timely recognition of generalised IIM developing following focal myositis may prompt the clinician to prescribe adequate treatment and thereby prevent damage and disability caused by the disease 3…”

Outbreak of Influenza B related to Benign Acute Childhood Myositis

“…Typically, patients with BACM complain of calf muscle pain after acute febrile illness, with CK elevation manifesting a few days later. BACM is often resolved within a few days without any complications, although recurrent myositis can develop 10,11) . All but one experienced calf muscle pain after febrile illness, with a median time interval between these manifestations of 3 days in this study.…”